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871.
Alcohols and their derivatives are ubiquitous and versatile motifs in organic synthesis. Deoxygenative transformations of these compounds are often challenging due to the thermodynamic penalty associated with the cleavage of the C−O bond. However, electrochemically driven redox events have been shown to facilitate the C−O bond cleavage in alcohols and their derivatives either through direct electron transfer or through the use of electron transfer mediators and electroactive catalysts. Herein, a comprehensive overview of preparative electrochemically mediated protocols for C−O bond activation and functionalization is detailed, including direct and indirect electrosynthetic methods, as well as photoelectrochemical strategies.  相似文献   
872.
The solvation shell is essential for the folding and function of proteins, but how it contributes to protein misfolding and aggregation has still to be elucidated. We show that the mobility of solvation shell H2O molecules influences the aggregation rate of the amyloid protein α-synuclein (αSyn), a protein associated with Parkinson's disease. When the mobility of H2O within the solvation shell is reduced by the presence of NaCl, αSyn aggregation rate increases. Conversely, in the presence CsI the mobility of the solvation shell is increased and αSyn aggregation is reduced. Changing the solvent from H2O to D2O leads to increased aggregation rates, indicating a solvent driven effect. We show the increased aggregation rate is not directly due to a change in the structural conformations of αSyn, it is also influenced by a reduction in both the H2O mobility and αSyn mobility. We propose that reduced mobility of αSyn contributes to increased aggregation by promoting intermolecular interactions.  相似文献   
873.
The elastic behavior of a material can be a powerful tool to decipher thermal transport. In thermoelectrics, measuring the elastic moduli—directly tied to sound velocity—is critical to understand trends in lattice thermal conductivity, as well as study bond anharmonicity and phase transitions, given the sensitivity of elastic moduli to the chemical bonding. In this review, we introduce the basics of elasticity and explain the origin of high-temperature lattice softening from a bonding perspective. We then review elasticity data throughout classes of thermoelectrics, and explore trends in sound velocity, anharmonicity, and thermal conductivity. We reveal how experimental sound velocities can improve the accuracy of common thermal conductivity models and present a critical discussion of Grüneisen parameter estimates from elastic moduli. Readers will be equipped with tools to leverage elasticity measurements or calculations to accurately interpret thermal transport trends.  相似文献   
874.
Herein, we report a Cu-mediated trifluoromethylation of carbonyl-type compounds and unactivated olefins enabled by visible-light irradiation via σ C(sp3)−C bond-functionalization. The reaction is distinguished by its modularity, mild conditions and wide scope—even in the context of late-stage functionalization—thus offering a complementary approach en route to valuable C(sp3)−CF3 architectures from easily accessible precursors.  相似文献   
875.
Fluoroarenes are abundant and readily available feedstocks. However, due to the high reduction potentials of mono-fluoroarenes, their photoreduction remains a continuing challenge, motivating the development of efficient activation modes to address this issue. This report presents the blue light-induced N-heterocyclic carbene (NHC)-catalyzed single electron reduction of mono-fluoroarenes for biaryl cross-couplings. We discovered that under blue light irradiation, NHC/tBuOK combination could construct powerful photoactive architectures to promote single electron transfer for Caryl−F bond reduction via forming highly reducing NHC radical anion. Notably, the strategy was also successful to reduce Caryl−O, Caryl−N, and Caryl−S bonds for biaryl cross-couplings.  相似文献   
876.
Selective functionalization of non-activated C(sp3)−H bonds is a major challenge in chemistry, so functional groups are often used to enhance reactivity. Here, we present a gold(I)-catalyzed C(sp3)−H activation of 1-bromoalkynes without any sort of electronic, or conformational bias. The reaction proceeds regiospecifically and stereospecifically to the corresponding bromocyclopentene derivatives. The latter can be readily modified, comprising an excellent library of diverse 3D scaffolds for medicinal chemistry. In addition, a mechanistic study has shown that the reaction proceeds via a so far unknown mechanism: a concerted [1,5]-H shift / C−C bond formation involving a gold-stabilized vinylcation-like transition state.  相似文献   
877.
Phenyl azides substituted by an (alkylphenyl)ethynyl group facilitate benzylic sp3(C−H) functionalization in the presence of a JohnPhosAu catalyst, resulting in indole-fused tetra- and pentacycles via divergent N- or C-cyclization. The chemoselectivity is influenced depending on the counter-anion, the electron density of the α-imino gold(I) carbene, and the alkyl groups stabilizing the benzylic carbocation originating from a 1,5-hydride shift. An isotopic labeling experiment demonstrates the involvement of an indolylgold(I) species resulting from a tautomerization that is much faster than the deauration. The formation of a benzylic sp3(C−H) functionalization leading to an indole-fused seven-membered ring is also demonstrated.  相似文献   
878.
A series of redox-responsive ferrocenyl-substituted boranes and boronic esters were synthesized. Oxidation of the ferrocenyl ligand to the ferrocenium resulted in a drastic increase in the Lewis acidity beyond the strength of SbF5, which was investigated experimentally and computationally. The resulting highly Lewis acidic boron compounds were used for catalytic C−F and S−F bond activation.  相似文献   
879.
Reversing the conventional site-selectivity of C−H activation provides efficient retrosynthetic disconnections to otherwise unreactive bonds. Described herein is the Brønsted acid-catalyzed reaction that selectively performs meta-amination of anisidines with aliphatic-, heterocyclic- and aromatic amines in a one-pot procedure. In addition to dramatically simplifying the synthesis of meta-substituted anilines, our approach has the advantage of the scalability and remarkable functional group tolerance, including late-stage functionalization of pharmaceutical compounds and natural products. The control experiments and detailed computational analysis provide insight into the reaction mechanism and the origin of meta-selectivity. The protocol extended to the synthesis of challenging tri-aminated arenes and successfully applied for the efficient synthesis of 5-HT6 receptor antagonists, the anti-psychotic drugs viz.. SB-214111, SB-258510, and specifically, anti-schizophrenic drug SB-271046.  相似文献   
880.
The Suzuki–Miyaura cross-coupling is one of the most important and powerful methods for constructing C−C bonds. However, the protodeboronation of arylboronic acids hinder the development of Suzuki–Miyaura coupling in the precise synthesis of conjugated polymers (CPs). Here, an anhydrous room temperature Suzuki–Miyaura cross-coupling reaction between (hetero)aryl boronic esters and aryl sulfides was explored, of which universality was exemplified by thirty small molecules and twelve CPs. Meanwhile, the mechanistic studies involving with capturing four coordinated borate intermediate revealed the direct transmetalation of boronic esters in the absence of H2O suppressing the protodeboronation. Additionally, the room temperature reaction significantly reduced the homocoupling defects and enhanced the optoelectronic properties of the CPs. In all, this work provides a green protocol to synthesize alternating CPs.  相似文献   
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